Lift truck



Feb. 1, 1955 G. u. BRUMBAUGH LIFT TRUCK 2 Sheet's-Sheet l Filed July l0,1952 INVENTQR.

GEORGE UB/QUMBAWH IIIIIIM ATTORNEY Feb. 1, 1955 G. u. BRUMBAUGH LIFTTRUCK 2 Sheets-Sheet 2 Filed July 1o, 14952 INVENTOR.

ATTORNEY United States Patent O LIFT TRUCK George U. Brumbaugh, PaloAlto, Calif., assigner to Peterbilt Motors Company, Oakland, Calif., acorporation of California Application July 10, 1952, Serial No. 298,159

6 Claims. (Cl. IS7- 9) This invention relates to improvements inattachments for lift trucks.

In particular the invention relates to a lifting mast arrangement whichmakes it possible for the carriage to lift a weight a substantial heightoff the oor with no increase in the height of the mast, while stillretaining operability of the mast to lift to its full lifting height.

One problem solved by this invention involves the heretofore existingrestricted use of lift trucks in the loading of freight cars and in likerestricted areas where the roof and door openings are not much higherthan the mast when the latter is in its down position.

Another problem solved is in arranging the lift cylinders so as to getfull lifting strength without having the pressure retained by the pistonrod packing.

Another problem solved is in providing a practical fool-proof devicewith just one control lever and by which the mast must be retractedbefore the carriage can be lowered.

Objects of the present invention are to provide for lifting the carriage(and supported freight) without lifting the mast; to provide asimplified free lift device with a minimum of parts and ease ofmanufacture and servicing; to provide means for lifting an object offthe floor (01' from high on a stack and then for lowering it and themast) so that entry can be made into a space where there is a lowceiling; and to provide other advantages which will become apparent fromthe following description.

Variations in structural details from the preferred embodiment describedherein pursuant to Revised Statutes No. 4888 are contemplated as beingincluded in the patent.

In the drawings:

Fig. l is an isometric diagrammatic broken away view of parts of thedevice (with the lift truck omitted) showing the carriage bracket at thetop of its free lift stroke, and with the three sections of the mast inpartially raised position;

Fig. 2 is a view in vertical section taken on the line 2-2 of Fig. l;

Fig. 3 is a similar view taken on the line 3-3 of Fig. 1;

Fig. 4 is a plan view partly in section taken on about the line 4 4 ofFig. 2, except that-the carriage is in its lowered position;

' Fig. 5 is a View in side elevation of the portion of the carriagewhich slides in the mast;

Fig. 6 is a diagrammatic View of the device with the carriage in itslowermost position;

Fig. 7 is a like view with the carriage at the top of its free liftposition and with the mast in its lowest position when working withinconfined areas;

Fig. 8 is a diagrammatic view showing the carriage and the mast raisedfull height; and

Fig. 9 is an enlarged detail of the piston rod packing and leakagereturn means.

While the device is illustrated with only the base portion of thecarriage shown, the stub shaft is adapted to support a clamp forhandling rolls of paper. A fork or other weight supporting means may besubstituted on the carriage. Also the device is shown adapted to bedetachably secured to the front end of the truck body because it may beused on any make of vehicle. The hydraulic valves, hose, and pressuresource to actuate the pistons in the lift cylinders are omitted becausesuch are well known in this art. Briey summarized, the pressure systembeyond the valve is connected to the inlet at the base of each liftcylinder where it works on a solid piston ICC with the usual packing.The operation will be described later. The invention has also to do withthe new and simplified combination of parts whereby the carriage ismounted in the channel of a plurality of nested mast sections and thelift cylinders are mounted in a novel manner within the confines of themast structure.

In the drawings, the carriage base plates 10 are shown secured to a faceplate 11 on which are secured the stub shaft 12 and the brackets 13 tosupport a set of paper clamping jaws so that a heavy roll of paper canbe held while being lifted about. The construction of these liftingclamps is now well known and no further description is necessary exceptto say that the driver may move the lift truck so the jaws are onopposite sides of a roll of paper and by moving suitable valve leversthe jaws Will clamp the roll of paper tightly enough to support it freeof the floor or other support.

The carriage base plates 10 have rollers 14 journaled on pins 15. Theserollers just tit inside the channels 16 of the inner channel section 17of the liftable mast 18. The carriage and rollers move up or down in thechannel track. The liftable mast 18 is made with the three nestedchannel sections 17, 19 and 20.

The outer mast section 20 is made up of the channel sections 20, 20 witha bottom cross member 21 and a cross member 22 near its upper end. Themast section 20 has the ears 23 with notches 24 to pivot the mast to anaxle shaft supported on the front end of the truck body. The upper endof the mast 20 :is supported near its tlcp by a brace (not shown) whichextends from the truc The inner section 17 of the mast is made up of thechannel sections 17 with a bottom tie cross member 25 welded securely tothe channel section 17 because it is on this base that the free liftcylinders 26 are fastened. A hole 27 is provided in this cross member 25with suflicient clearance to run free of the main mast lift cylinder 28which extends through it and is fastened to the base 21.

The mid section 19 of the mast is made up of the channel sections 19which are tied at the top by the cross member 29 having thestrengthening tubular member 30 and the extension 31 which extends inbetween the free lift chains and over the main cylinder 28. No crossmember is needed at the base of the mid section 19 as its slides betweenthe channels 17 and 20. The mast sections 17, 19 and 20 have a freesliding t with each other so they move up and down without substantialresistance.

Fig. 3 shows the chains 32 by which the carriage 10 is lifted andlowered in the inner mast section 17. Each chain is secured at 33 to thecross tie 25 and at 34 to the carriage plate 10. Between these pointseach chain is passed over its sheave 35 mounted on the end of the ramrod 36 of each free lift cylinder 26. In Fig. 3, the free lift is shownextended its full length which has brought the carriage to the top ofthe channel section 17. The piston 37 is shown in the cylinder 26. Fluidunder pressure is introduced and removed through. the fitting 38.

Fig. 2 shows the chains 39 and mast lift cylinder 28 by which the mastsections are extended and lowered. The chains 39 are secured at 40 tothe cross tie of the inner mast section 17 and at 41 to the cross tie 22of the outer mast section 20. The cylinder piston rod 42 has a crosshead 43 with sheaves 44 over `which the chains pass. The cross head 43preferably is secured to the under side of the cross member 31 of themid mast section 19. The piston 45 is shown at the bottom of Fig. 2. Thenet result of this compact and eicient structure is that the mid-mastsection 19 is always kept in an evenly spaced position vertically inrelation to the inner and outer mast sections 17 and 20 because it ismoved positively by the piston rod 42. The two to one lifting ratio ofthe sheaves 44 in relation to the inner mast section 17 means that thelatter moves up twice as fast as the mid section 19.

Fluid pressure to effect movement of the piston 45 enters and exitsthrough the fittings 46.

An important improvement in the present device over the prior art is inhaving the lifting pressure introduced against a solid piston and havingno lifting pressure applied against the seals around the piston rods.What small amount of oil escapes past the pistons 37 or 45 is bled offthrough the ttings 49. This arrangement is shown in Figs. 2, 3, and inFig. 9 where the upper end of one of the free lift cylinders 36 is shownwith its piston rod 36 extending beyond the end of the cylinder. Thepacking 47 need only seal the uid against atmospheric pressure becausethere is no pressure in the area 48 above the piston and the bleedconnection 49 carries back to the iluid reservoir which is atatmospheric pressure. The same arrangement is used on the mast liftcylinder and its piston rod.

The combined area of the pistons in the free lift cylinders 26 isgreater than the area of the piston in the mast lift cylinder 28. Sincethere is a common connection to the ttings 33, 46 on all the cylindersand a single control valve to control the admission of tluid thereto,the result is that the free lift will be actuated for its full liftingstroke before the mast will lift and on opening of the control valve torelease the lluid pressure, the mast will come down ahead of thecarriage. This is an important operating characteristic because itremoves all choice from the operator who, with certain earlier types ofdevices, could drop the carriage before the mast was down. Not only isthe present device fool-proof from an actuation standpoint, but it alsois constructed so the lifting pressure does not canse trouble with thepackings.

Figs. 6, 7 and 8 are only diagrammatic to show typical positions of thelift parts. lowest position and the carriage is at its lowest position.In Fig. 7 only the carriage 10 has been raised to the top of its travelin the channel 17 by the full stroke of its rams 26. The mast remains atits lowest position so there can be free access through doors or intocars with low overhead clearances. In Fig. 8 the mast has been extendedto its full height by the ram 28 as when depositing or picking up anobject high on a stack.

The invention gives great ilexibility of operation to the device andmakes possible its use in very confined spaces with low verticalclearance, and yet it enables hehoperator to deposit or to pick upobjects several tiers The sheaves 35 illustrated in this description maybe sprockets, rollers, or any other form of anti-friction support for achain or cable by which the carriage is raised or lowered.

What is claimed is:

l. In a mast for a lift truck the combination of a three sectionextensible mast of nested channel sections, a mast-lift cylinder andram, free-lift cylinders, mast lift chains, and free lift chains; inwhich the outer section has a bearing means at the bottom adapted toengage the truck on which it is mounted, a bottom cross member on whichthe mast lift cylinder is secured, and a top cross member; the midsection has a cross member near its top and to which the ram of saidmast lift cylinder is secured; the inner section has a cross member nearits top, a bottom cross member on which the free lift cylinders aremounted and the free lift chains and the mast lift chains are secured; acarriage slidable in the channel of said inner mast section, andconnected to one end of said free lift chains; a ram in each free liftcylinder, each having a sheave over which said free lift chains extend;a cross-head on said mast lift cylinder ram near its point of attachmentto said mid mast section, with a sheave on each side of said cross-headover which said mast lift chains extend; and means for introducing iluidunder pressure into said cylinders to cause the rams therein to moveupwardly.

2. The device of claim l in which the ram in each cylinder is a solidpiston.

3. The device of claim 2 in which the top of each cylinder is providedwith an outlet through which any fluid that leaks past the piston may bevented from the cylinder.

4. The device of claim l in which said mast lift ram projects through anopening provided in the bottom cross member of said inner mast sectionand said cylinders are all contained within the contines of said nestedchannel mast sections.

5. A mast for a lift truck adapted to position all its lifting apparatussubstantially along a single vertical In Fig. 6, the mast is at itsplane closely adjacent the front axle of the truck, including incombination: an extensible mast having an outer section, a midsectionnested in said outer section, and an inner section nested in saidmidsection; said outer section having a bottom cross member with arearwardly-extending bearing means adapted to engage the truck axle onwhich the mast is mounted, a pair of parallel upwardly-extendingchannels secured to said bottom cross member, and a top cross memberjoining together the rear surfaces of said channels; said midsectionhaving a pair of parallel, upwardly-extending channels nested forvertical movement in the channels of said outer section, and a singlecross member extending across its said channels near its top; said innersection having a pair of parallel upwardly-extending channels nested inthe channels of said midsection, a cross member adjacent its top, and abottom cross member with an opening therethrough; a mast lit't cylindersecured on the bottom cross member of said outer section and extendingup through the opening in the bottom cross member of said inner sectionwhen the inner section is in its lower position, with its ram secured tothe cross member of said midsection, so as to be enclosed within saidmast; a pair of free-lift cylinders mounted on the bottom cross memberof said inner section, each said free-lift cylinder having a ram with asheave thereon, said free-lift cylinders also lying within the confinesof said mast; a carriage slidable in the channels of said inner mastsection; free-lift chains extending over said sheaves, having one endsecured to the bottom cross member of said inner mast section and itsopposite end connected to said carriage; a cross head on said mast liftcylinder ram near its point of attachment to said mast midsection, witha sheave on each side of said cross-head; mast lift chains extendingover said sheaves and each secured at one end to the bottom cross memberof said inner mast section and at the other end to the top cross memberof said outer mast section, whereby said midsection is always keptevenly spaced vertically in relation to the inner and outer mastsections so as to atord the maximum in stability; and means forintroducing uid under pressure into said cylinders to cause the ramstherein to move upwardly, all the lifting being donel along what issubstantially the vertical plane of said mast.

6. A mast for a lift truck including in combination: a three-sectionextensible mast with the sections comprising nested channels, the outersection having a bottom cross member with a rearwardly-extending bearingmeans securable to the truck on which the mast is mounted and a topcross member, the midsection having a single cross member extendingacross its channels near its top, and the inner section having a crossmember adjacent its top and a bottom cross member; rst extensible powermeans secured on the bottom cross member of said outer section with itsram secured to the cross member of said midsection, so as to be enclosedwithin said mast; a pair of free-lift extensible power means mounted onthe bottom cross member of said inner section, each said free-lift meanshaving a ram with rotatable means thereon, said free-lift means alsolying within the contines of said mast; a carriage slidable in thechannels of said inner mast section; free-lift non-expansible flexiblelinking means extending over said rotatable means, having one endsecured to the bottom cross member of said inner mast section and itsopposite end connected to said carriage; cross means on said firstextensible power means near its point of attachment to said mastmidsection, with rotatable means on each side of said cross means;mast-lift non-expansible flexible linking means extending over saidrotatable means and each secured at one end to the bottom cross memberof said inner mast section and at the other end to the top cross memberof said outer mast section; and means for extending said extensiblemeans to cause their rams to move upwardly.

Guerin May 7, 1946 Lehman Jan. 22, 1952

